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Asphalt Mix Performance Testing for Warm Mix Asphalt Field Project on
Ministry of Transportation Ontario Highway 10
Selena Lavorato, B.Sc., C.E.T.
Quality Systems Manager
Coco Asphalt Engineering
949 Wilson Ave
Toronto, Ontario
Tel. 416-633-9670
Fax: 416-633-5318
Email: [email protected]
Steve Manolis, P.Eng.
General Manager
Coco Asphalt Engineering
949 Wilson Ave
Toronto, Ontario
Tel. 416-633-9670
Fax: 416-633-5318
Email: [email protected]
Andrew Pahalan, C.E.T.
Quality Control Manager
Coco Paving Inc.
949 Wilson Ave
Toronto, Ontario
Tel. 416-633-9670
Fax: 416-633-5318
Email: [email protected]
Ryon Reid
Product Development Specialist
Coco Paving Inc.
949 Wilson Ave
Toronto, Ontario
Tel. 416-633-9670
Fax: 416-633-5318
Email: [email protected]
Submission date: June 1st, 2011
Word count: 3,986
.
LAVORATO, MANOLIS, PAHALAN & REID 2
ABSTRACT
A warm mix asphalt (WMA) paving project utilizing HyperTherm® WMA technology was completed on
Highway 10 in Ontario with a 2,500 tonne hot mix asphalt (HMA) control section using Superpave 12.5
mm FC2 mixes produced with PG 64-28 binder.
Plant produced samples HMA and WMA samples achieved acceptable rutting results with the
HMA achieving nominally better results when tested with the Asphalt Pavement Analyzer. Acceptable
moisture sensitivity results were obtained for both the HMA and WMA.
Fatigue cracking properties measured with the Four Point Bending Beam Fatigue Test, and low
temperature cracking properties tested with the Thermal Stress Restrained Specimen Test and Bending
Beam Rheometer, were significantly improved in the WMA compared to the HMA. Samples were long
term oven aged to simulate field aging.
Dynamic modulus testing showed that WMA had lower dynamic modulus values than HMA and
agreed with the trends identified during rutting and fatigue cracking tests.
LAVORATO, MANOLIS, PAHALAN & REID 3 INTRODUCTION Warm Mix Asphalt (WMA) continues to gain acceptance as a viable technology across North America.
This technology enables the production and placement of asphalt mixes at temperatures that are lower
than those of Hot Mix Asphalt (HMA). Performance benefits include improved mix workability and
compaction, the ability to extend haul distances and to work in cooler weather, and improvements in
various pavement rehabilitation methodologies (1).
HyperTherm®, which was used on this particular field project, is a non-aqueous chemical warm
mix additive that allows for lower mixing and compaction temperatures without significantly affecting the
physical properties of the bitumen binder. It has been used in the prior projects as a cool weather
compaction aid, (2) workability aid for mixes with high RAP content (3) and other projects across Ontario
and other parts of Canada (4, 5) and the United States. HyperTherm® is known as QualiTherm in the
United States.
The objectives of this paper were to evaluate mix performance properties that relate to rutting,
fatigue, moisture sensitivity, and low temperature cracking of WMA as compared to HMA.
SCOPE
The project involved placing a 5,190 tonne WMA surface course with a 3,700 tonne HMA control section
using a Superpave 12.5 mm FC2 mix. The surface courses were placed to a compacted thickness of 40
mm and used polymer modified PG 64-28 as the asphalt cement. Prior to placing the surface courses, the
existing pavement was milled out to a depth of 40 mm and replaced with a 50 mm Superpave 19 mm
HMA binder course for the entire length of the project using PG 64-28 asphalt cement. All mixes were
designed for Traffic Category D (10 to 30 million Equivalent Single Axle Loads or ESAL’s) (6) on the
Ministry of Transportation Ontario (MTO) project.
Figure 1 outlines the limits of the contract which extended from the Highway 410 connection to
Highway 10 northerly to Peel Road 9 (King Street).
FIGURE 1. WMA and HMA Sections on Highway 10
Warm Mix Section
Hot Mix Section
4 A combination of empirical and mechanistic asphalt mix performance tests were performed on
plant produced field samples in order to assess properties relating to rutting, fatigue, moisture sensitivity,
and low temperature cracking. A visual assessment of field performance was completed on the WMA and
HMA sections on Ontario Provincial Highway 10 after one winter and approximately nine months in
service.
MIX DESIGN AND BINDER PROPERTIES Table 1 shows the Performance Graded Asphalt Cement (PGAC) properties of the PG 64-28 PMA binder
with and without HyperTherm®. Both binders met the required AASHTO M320 (7) specifications. A
minor reduction in high temperature PGAC properties accompanied by a minor improvement in low
temperature PGAC properties were noted after the addition of HyperTherm®.
TABLE 1. Superpave Binder Data for PG 64-28 PMA and PG 64-28 PMA HyperTherm®
Sample PG 64-28 PMA
PG 64-28 PMA
with 0.2%
HyperTherm®
AASHTO
M320
Specification
Original Binder
Rotational Viscosity @ 135oC (Pa.s)
@ 165oC
0.718
0.135
0.667
0.130
≤ 3.0
DSR, G*/sinδ @ 64oC (kPa)
@ 70oC (kPa)
1.246
0.750
1.135
0.642
≥ 1.0
RTFO Residue (AASHTO T240)
Mass Change (%) 0.202 0.303 ≤ 1.0
DSR, G*/sinδ @ 64oC (kPa)
@ 70oC (kPa)
2.354
1.115
2.372
1.164
≥ 2.2
PAV Residue (AASHTO R18)
Aging Temperature (oC) 100 100 100
DSR, G* x sinδ @ 22oC (kPa)
@ 19oC (kPa)
2,777
3,590
2,228
3,525
≤ 5000
Bending Beam Rheometer
Creep Stiffness @ -18oC (MPa)
@ -24oC (MPa)
Slope, m-value @ -18oC
@-24oC
193
353
0.330
0.271
170
341
0.339
0.275
≤ 300
≥ 0.300
Performance Grade PG 66.6-30.9 PG 65.3-31.5
The Superpave 12.5 mm FC2 mix used in this project was designed using a Superpave Gyratory
Compactor (SGC) with 100 gyrations. Identical material proportions were utilized for both the WMA and
HMA designs with the exception that the warm mix contained 0.2 percent HyperTherm® by weight of
the binder. The HMA was mixed at 155oC and compacted at 145
oC. Mixing and compaction
temperatures for the WMA were 130oC and 110
oC respectively.
Similar volumetric properties were obtained for both the WMA and the HMA. The mix design and
volumetric properties for the 12.5 mm FC2 mixes used in this project are presented in Tables 2 and 3.
LAVORATO, MANOLIS, PAHALAN & REID 5 TABLE 2. Superpave 12.5mm FC2 Mix Design Utilized on Highway 10
Material Source
HMA 12.5mm FC2
PG 64-28 PMA
(%)
WMA 12.5mm FC2
PG 64-28 PMA
HyperTherm®
(%)
HL1 Stone Danford Aggregates 44.0 44.0
Manufactured Sand IKO 22.0 22.0
Screenings Danford Aggregates 34.0 34.0
PG 64-28 PMA with
0.2% HyperTherm® by
weight of binder
Coco Asphalt
Engineering
--
5.2
PG 64-28 PMA Coco Asphalt
Engineering 5.2 --
TABLE 3. Highway 10 Superpave 12.5mm FC2 Mix Design and Volumetric Properties
Property
HMA
12.5 mm FC2
PG 64-28 PMA
WMA
12.5 mm FC2
PG 64-28 PMA
HyperTherm®
OPSS 1151
Specification
Mixing Temperature (oC) 155 130
Compaction Temperature (oC) 145 110
Bulk Relative Density 2.351 2.371
Maximum Relative Density 2.465 2.469
Air Voids (%) 4.6 4.0 3 – 5
Voids in Mineral Aggregate (%) 16.0 15.1 ≥ 14.0
TSR (%) 92 81 ≥ 80
Dust to Binder Ratio 1.1 1.2 0.6 – 1.2
Gmm @ Nini (8 Gyrations) (%) 88.9 88.9 ≤ 89.0
Gmm @ Ndes (100 Gyrations) (%) 96.0 96.0 96.0
Gmm @Nmax (160 Gyrations) (%) 96.9 96.9 ≤ 98.0
PRODUCTION AND PLACEMENT Paving of the 2,500 tonne HMA section took place during the week of September 10, 2010. Production
and placement of the 5,190 tonne WMA section occurred during the following week. Both asphalt mixes
were produced at the Coco Paving Wolfedale asphalt plant in Mississauga, Ontario. A Material Transfer
Vehicle (MTV) and standard paver were utilized for this job. Compaction for both the warm mix and hot
mix sections was achieved using 10 tonne vibratory steel drum rollers, followed by a 19 tonne pneumatic
tired roller and a 10 tonne static steel finish roller. The 12.5 mm FC2 mixes were placed in one lift with a
compacted thickness of 40 mm.
Field compaction results ranged between 92 to 93 percent for the HMA and between 92 to 95
percent for the WMA (based on theoretical Maximum Relative Density). Mixing temperatures ranged
between 145 – 155oC for the HMA and 125 – 145
oC for the WMA. The compaction temperature was
approximately 145oC for the HMA and 110
oC – 125
oC for the WMA.
6
FIGURE 2. Construction of 12.5 mm FC2 WMA Section on Highway 10
FIGURE 3. Construction of 12.5 mm FC2 HMA Section on Highway 10
LAVORATO, MANOLIS, PAHALAN & REID 7
FIGURE 4. Coco Paving Wolfedale Asphalt Plant in Mississauga, Ontario
PERFORMANCE TESTING
Overview
Asphalt mix performance tests were conducted on plant produced samples taken from the field in order to
compare the rutting, moisture sensitivity, fatigue, and low temperature properties of the WMA and HMA.
Rutting resistance was measured in a loaded wheel test using an Asphalt Pavement Analyzer
(APA). Moisture sensitivity properties were evaluated by calculating the Tensile Strength Ratio (TSR).
Samples used to evaluate fatigue and low temperature cracking properties were subjected to long term
oven aging for five days prior to testing in order to simulate aging of the asphalt mix in the field. A Four
Point Bending Beam Flexural Fatigue Test was used to evaluate fatigue properties. The Thermal Stress
Restrained Specimen Test (TSRST) was utilized to measure low temperature cracking properties. Low
temperature mix properties were also evaluated using the Bending Beam Rheometer (BBR) to measure
the stiffness of thin beams of asphalt mix at low temperatures.
Dynamic Modulus testing was completed over a range of temperatures and frequencies as a
complement to the tests described above.
Rutting Resistance
An evaluation of rutting resistance was completed on the WMA and HMA samples using the Asphalt
Pavement Analyzer (APA) as per AASHTO T340-10 (8). In this test a loaded wheel is placed on a
pressurized linear rubber hose which rests on the test specimen. The wheel cycles back and forth for
8,000 cycles. The resulting rut depth is measured as against the number of cycles (9).
8 Field samples were compacted to 7.0 ± 0.5 percent air voids using a SGC. Samples were
conditioned for a minimum of six hours at 58oC prior to testing. Rut testing was completed at 58
oC which
is the environmental high temperature grade for the climatic region in which the project was paved.
Results are presented in Table 4 below.
TABLE 4. APA Rut Depth of WMA and HMA Field Samples
Mix Mean Rut Depth
(mm) Standard Deviation
Number of
Samples
12.5 mm FC2 WMA 5.25 0.23 4
12.5 mm FC2 HMA 4.57 0.73 4
Average rut depths after 8,000 cycles for the HMA and WMA samples were 4.57 mm and 5.25 mm
respectively. Both mixes met the maximum 8 mm rut depth at 8,000 wheel load cycles recommended by
the National Center for Asphalt Technology (NCAT) (10). The WMA exhibited nominally more rutting
than the HMA. A study completed in 2009 found that 12.5 mm FC2 WMA and HMA placed on ramps
leading to and from Ontario Provincial Highway 401 and on streets in the City of Hamilton both produced
acceptable APA rutting results with the HMA exhibiting nominally better rut depths than the WMA (4).
Fatigue Properties
Flexural fatigue properties were evaluated using the Four Point Bending Beam Test as per AASHTO
T321-07 (11). An Asphalt Vibratory Compactor (AVC) was used to compact field samples of asphalt
mix to 7.0 +/- 0.5 percent air voids. The compacted field samples were then cut into beams measuring
62.5 mm by 50 mm by 375 mm. Samples were subjected to long term oven aging by conditioning them
for 5 days at 85oC prior to testing in order to simulate long term aging of the mix in the field (12).
A Material Testing System (MTS) test frame equipped with an environmental chamber was used to
conduct the flexural fatigue testing. The test was run in constant strain mode in which the stress applied
to the beams decreased with the number of cycles in order to maintain constant strain. Samples were
cycled through repeated sinusoidal loads with a 0.1 second load time and 0.4 second rest time. Fatigue
life was defined in terms of the number of cycles required to reach 50 percent of the initial beam stiffness
(14, 15). Testing was completed at 20 +/- 0.5oC. Figure 5 illustrates the flexural fatigue test procedure.
LAVORATO, MANOLIS, PAHALAN & REID 9
FIGURE 5. Four Point Bending Beam Flexural Fatigue Test
Flexural fatigue test results are summarized in Table 5 below. This is a 58 percent improvement in
the flexural fatigue results for the WMA as compared to the HMA. A 2009 study also found that 12.5
mm FC2 WMA mixes placed on ramps leading to and from Ontario Provincial Highway 401 and on
streets in the City of Hamilton had better flexural fatigue properties than the corresponding HMA mixes
(4).
TABLE 5. Flexural Fatigue Test Data
Initial Stiffness (MPa) Cycles to Failure (Nf50)
Mix Mean
Standard
Deviation
Number
of
Samples
Mean Standard
Deviation
Number
of
Samples
12.5 mm FC2 WMA 4,407 188 5 315,378 59,300 5
12.5 mm FC2 HMA 4,829 339 5 198,971 65,371 5
Moisture Sensitivity Plant produced field samples were evaluated for moisture sensitivity by testing the TSR (AASHTO T283)
of each mix (13). Both the 12.5 mm FC2 HMA and WMA met the 80 percent minimum requirement for
TSR in the Province of Ontario (6). The 12.5 mm FC2 HMA achieved an average TSR value of 92
percent which was higher than the average TSR result of 82 percent obtained for the 12.5 mm FC2 WMA.
Load Load
Deflection
Reaction Reaction
Returns to Original Position
Asphalt
Mixture
Fatigue
Beam
Specimen
10
Dynamic Modulus A dynamic modulus characterization of the 12.5 mm FC2 WMA and HMA plant produced samples was
completed using AASHTO TP 62-07 (14) as a guide.
Dynamic modulus (E*) is an indicator of the stiffness of the mix and is the absolute value of the
peak-to-peak stress divided by the peak-to-peak recoverable strain under sinusoidal loading. The phase
angle (δ) describes the degree to which the mix is behaving as an elastic or viscous material. In a purely
elastic material, the applied stress and resulting strain response occur in phase, or simultaneously, with
each other. Asphalt is characterized as a viscoelastic material with phase angles in between zero and 90
degree (15).
An MTS test frame equipped with an environmental chamber was used to conduct dynamic
modulus testing over a range of temperatures (-10, 4, 21, and 37oC) and frequencies (0.1, 1, 5, 10, and
25Hz). A SGC was used to prepare asphalt briquettes at 7.0 +/- 0.5 percent air voids. Cylindrical test
samples measuring 100 mm in diameter by 150 mm in height were cored out of 150 mm diameter SGC
briquettes using a water cooled coring machine with a diamond coring bit. Strain gauges were affixed to
the test specimens and used to measure strain under sinusoidal loading conditions in order to calculate
dynamic modulus and phase angle data.
The principle of time-temperature superposition allows that if asphalt is treated as a linear
viscoelastic material then the dynamic modulus at a given temperature and frequency may also be
obtained at another temperature and frequency combination. This technique allows for the creation of a
master curve in which dynamic modulus data points obtained at different temperatures are shifted to
either higher or lower frequencies so that the resulting curve shows dynamic modulus results at a single
reference temperature.
The frequency to which each data point was shifted is called a reduced frequency and was
calculated by dividing the frequency at which the data point was collected at by a shift factor as shown in
equation 1 below:
fr = Ts
f (1)
fr = reduced frequency,
sT = shift factor according to temperature, and
f = frequency.
Equation 2 below was used to create and fit the master curves at the reference temperature of 21oC.
This equation was developed by Pellinen and used in research conducted by Clyne et al. (15) in a joint
study between the University of Minnesota and the Minnesota Department of Transportation (DOT).
log |E*| = δ +
))(log(1 Tr sf
e+−+ γβ
α (2)
log |E*| = log of dynamic modulus,
δ = minimum modulus value,
sT = shift factor according to temperature,
α = span of modulus values,
β, γ = shape parameters, and
fr = reduced frequency.
LAVORATO, MANOLIS, PAHALAN & REID 11 Figures 6 and 7 illustrate the creation master curves for the 12.5 mm FC2 HMA and WMA mixes
examined in this study. Master curves were created at a reference temperature of 21oC. Dynamic
modulus data that was collected at temperatures which are lower than the reference temperature (-4oC and
10oC) were shifted to the right towards higher frequencies. Likewise dynamic modulus values that were
collected at 37oC, which is higher than the reference temperature, were shifted to the left towards lower
frequencies.
1.0.E-01
1.0.E+00
1.0.E+01
1.0.E+02
1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Frequency, Hz
Dyn
am
ic M
od
ulu
s |E
*|, G
Pa
-10°C HMA 4°C HMA 21°C HMA 37°C HMA HMA Fit
FIGURE 6. Dynamic Modulus Master Curve for 12.5 mm FC2 HMA
12
1.0.E-01
1.0.E+00
1.0.E+01
1.0.E+02
1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Frequency, Hz
Dyn
am
ic M
od
ulu
s |E
*|, G
Pa
4°C WMA 21°C WMA 37°C WMA WMA Fit -10°C WMA
FIGURE 7. Dynamic Modulus Master Curve for 12.5 mm FC2 WMA
A comparison between the master curves for the 12.5 mm FC2 WMA and HMA is shown Figure 8.
The master curves illustrate that the 12.5 mm FC2 WMA has lower dynamic modulus values and is less
stiff than the 12.5 mm FC2 HMA across the range of frequencies covered by the curves. Witczak et al.
have reported that dynamic modulus correlates to rutting and fatigue properties in the mix (16). The
results imply that at higher temperatures the HMA would have better rutting resistance than the WMA
since it is a stiffer material. At intermediate and low temperature the WMA is also less stiff than the
HMA which implies improved fatigue cracking properties. The APA rutting evaluation discussed earlier
in this report found that the both the WMA and the HMA had acceptable rutting resistance with the WMA
exhibiting nominally more rutting than the HMA. Flexural fatigue properties evaluated using the Four
Point Bending Beam Fatigue test were found to be significantly improved in the WMA as compared to
the HMA.
LAVORATO, MANOLIS, PAHALAN & REID 13
1.0.E-01
1.0.E+00
1.0.E+01
1.0.E+02
1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08
Frequency, Hz
Dy
nam
ic M
od
ulu
s |E
*|, G
Pa
-10°C HMA 4°C HMA 21°C HMA 37°C HMA HMA Fit
-10°C WMA 4°C WMA 21°C WMA 37°C WMA WMA Fit
FIGURE 8. Dynamic Modulus Master Curve for 12.5 mm FC2 WMA and HMA
Figure 9 below depicts the shift factors that were used to calculate the reference frequencies for the
creation of the dynamic modulus master curves. The shift factors for the 12.5 mm FC2 WMA and HMA
at the reference temperature of 21oC are zero indicating that the data that that was at the reference
temperature did not shift.
14
-2
-1
0
1
2
3
4
5
6
-10 -5 0 5 10 15 20 25 30 35 40
Temperature (C)
Sh
ift
Fa
cto
r
WMA
HMA
FIGURE 9. Shift Factors for 12.5 mm HMA and WMA Dynamic Modulus Master Curves
Thermal Stress Restrained Specimen Test (TSRST) Resistance to low temperature thermal cracking was evaluated using the Thermal Stress Restrained
Specimen Test (TSRST, AASHTO TP10-93). WMA and HMA field samples were compacted to 7.0 +/-
0.5 percent air voids using an AVC and then cut into 50 mm x 50 mm x 250 mm beams with a circular
saw. The specimens were long term oven aged prior to testing (12). Plates were affixed to the ends of the
specimen beams and the set up was inserted into an MTS test frame enclosed in an environmental
chamber for testing. Samples were conditioned at 5oC for six hours prior to testing. After conditioning,
an initial tensile load was applied and the temperature was reduced at a rate of 10oC
per hour. Thermal
contraction along the vertical axis of the specimen beams was monitored electronically during which the
system incrementally re-established the initial length of the specimen beams by adjusting the positioning
of the end plates affixed to the sample. This process continued until the internal stresses in the samples
increased to a level that caused tensile fracture of the specimen (17).
TABLE 6. Thermal Restrained Specimen Tensile Strength Test Results
Fracture Temperature (oC) Fracture Strength (kPa)
Asphalt Mix Type Mean
Standard
Deviation Mean
Standard
Deviation
Number of
Samples
12.5 mm FC2 HMA -25.4 2.6 586 88 5
12.5 mm FC2 WMA -29.8 1.6 598 63 5
The mean fracture temperature for the WMA was -29.8oC compared to -25.4
oC for the HMA (see
Table 8 above). Lower mixing temperatures during plant production which reduced the short term aging
that the binder experienced are likely accounting for the improved low temperature cracking properties.
LAVORATO, MANOLIS, PAHALAN & REID 15 Marasteanu et al. report that fracture temperature is a better indicator low temperature cracking
properties than fracture strength (17).
Low Temperature Flexural Creep Stiffness
In order to further examine low temperature thermal cracking properties, thin beams of asphalt mix were
tested for flexural creep stiffness at low temperature using the Bending Beam Rheometer (BBR) (17).
The testing methodology for mixture stiffness determination paralleled that used to determine the flexural
creep stiffness of asphalt cement binders (18). A greater load was applied to the asphalt mixture beams
than is used when testing asphalt cement binder beams in order to account for the higher stiffness of
asphalt mixtures as compared to asphalt cement binders.
Field samples of WMA and HMA were compacted in cylindrical moulds to 7.0 ± 0.5 percent air
voids with the SGC. Rectangular beams measuring 6.35mm thick x 12.7mm wide x 127mm long were
cut from the cylindrical specimens prepared with the SGC and long term oven aged (15). A Canon
Instrument Company BBR was used to test the asphalt mixture specimens at -18oC under a constant load
of 4,413± 50 mN applied to the midpoint of the beam for creep stiffness. Creep stiffness relates to the
stress built up in asphalt mixtures under low temperature conditions. Figure 10 depicts a photograph of
the thin asphalt mixture beams used in this test procedure. This is followed by figure 11 which illustrates
the low temperature flexural creep stiffness test using the BBR.
FIGURE 10. Thin Asphalt Mixture Beams Tested with Bending Beam Rheometer
16
FIGURE 11. Low Temperature Flexural Creep Stiffness Using the Bending Beam Rheometer
Table 9 below summarizes the low temperature creep stiffness results obtained on the asphalt
mixture beams at -18oC. The creep stiffness results support the potential for improved low temperature
cracking properties in the WMA as compared to the HMA.
TABLE 7. Bending Beam Rheometer Asphalt Mixture Test Results
Creep Stiffness at -18oC and 60s
(MPa) Asphalt Mix Type
Mean Standard Deviation
Number of Samples
12.5 mm FC2 HMA 8,200 104 4
12.5 mm FC2 WMA 7,667 87 4
FIELD PERFORMANCE
Both the 12.5 mm FC2 WMA and HMA sections of Highway 10 appeared to be performing similarly and
relatively distress free during a site visit after nine months including one winter in service. Figure 13
shows the surface texture of the HMA and WMA mats while Figure 14 depicts sections of the HMA and
WMA portions of Highway 10.
Thermal Fluid
-18 ºC
Support
Asphalt Mixture
Beam Sample
Test Load: 4, 431 mN
LAVORATO, MANOLIS, PAHALAN & REID 17
FIGURE 12. Surface Texture of WMA and HMA Pavements on Highway 10
FIGURE 13. HMA and WMA 12.5 mm FC2 Pavement Sections on Highway 10
FINDINGS AND RECOMMENDATIONS Performance testing was completed on plant produced samples of 12.5 mm FC2 WMA and HMA on
Ontario Provincial Highway 10. Polymer modified PG 64-28 asphalt cement was modified with
HyperTherm® for the WMA portion of the project. It was found that:
• Both HMA and WMA produced acceptable rutting results when tests with the APA.
• Long term oven aged samples of WMA provided significantly improved flexural fatigue
properties as compared to HMA when evaluated using the Four Point Bending Beam Fatigue test.
• An evaluation of moisture sensitivity properties showed that both the WMA and HMA met the
minimum 80 percent TSR requirement for the Province of Ontario with the HMA achieving higher
TSR results than the WMA.
• Dynamic modulus testing showed that the HMA had higher modulus values and was stiffer than
the WMA towards higher temperatures indicating the potential for better rutting resistance in the
HMA as compared to the WMA. At intermediate and lower temperatures the WMA had lower
modulus values and was less stiff than the HMA indicating a potential improvement in fatigue
cracking properties in the WMA as compared to the HMA.
• An evaluation of low temperature cracking properties with the TSRST on long term oven aged
samples showed that the WMA demonstrated improved low temperature properties with a critical
cracking temperature that was 4.4oC lower than the HMA samples. Further testing with the BBR on
thin beams of long term oven aged mixes found that the WMA had better low temperature flexural
fatigue properties than the HMA suggesting improved resistance to low temperature cracking.
• Both the WMA and HMA sections on Highway 10 exhibited similar and acceptable performance
after nine months including one winter in service.
HMA
HMA
WMA
WMA
18 REFERENCES
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14 American Association of State Highway and Transportation Officials (AASHTO) TP62-07.
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18 American Association of State Highway and Transportation Officials (AASHTO)T313-10.
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